I'll explain. There is a lot of debate on what defines masculinity. Wide midface, vs forward midface. Long jaw vs wide jaw. Often we here 'strong jawline.' But what foes it mean? I don't actually know, but I do know how one conception of 'jaw line' actually has more to do with chewing and facial muscles than bone.
Check this out: here are two examples of what some consider a strong jaw.
Notice the hollow cheecks. That means the bone actually doesn't go out that far (or else the cheeks wouldn't actually be hollow). What extends the skin outward in these cases is actually jaw muscle. Turns out there is a way to build extra jaw muscle via chewing exercises
A company makes these little white chewing tools that are used 10 min a day as a face workout. You can see a before and after shot above.
The other thingthat affects this is orthodontics. Teeth angled inwards on the jaw cause the bone to touch the skin before the tooth. Making a line. If the teeth are straight up and down on the bone, then the teeth touch the cheeck before the bone.
The other notion of 'strong jawline' is width. For example, Will Smith was rated as having the most masculine face possible in one study on male facial attractiveness.
He has no hollow cheecks, nor sharp angles, but a very wide midsection. And a wide jawline. Dwayne Wade is another example. (They also have large noses, which is also a male trait).
In this way, I actually believe the chiseled jaw look is actually a feminine face. Especially considering they also have small straight noses.
But look for female faces and that's all over the map too.
Asian girls have wide midsections amd wide jaws. Euro girls have longer jaws and narrower faces, unless they're latin. Latin girls have wide jaws.
Some girls have narrow chins, some dramatic, some recessed and some long like a horse.
Ultimately, I'm begining to believe that jaw bone structure is more determined by race and ethnicity more than sexual dimorphism. Any thoughts on this are welcome.